Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932583AbVKWWVG (ORCPT ); Wed, 23 Nov 2005 17:21:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932585AbVKWWVG (ORCPT ); Wed, 23 Nov 2005 17:21:06 -0500 Received: from nevyn.them.org ([66.93.172.17]:45230 "EHLO nevyn.them.org") by vger.kernel.org with ESMTP id S932583AbVKWWVC (ORCPT ); Wed, 23 Nov 2005 17:21:02 -0500 Date: Wed, 23 Nov 2005 17:20:56 -0500 From: Daniel Jacobowitz To: Linus Torvalds Cc: Alan Cox , "H. Peter Anvin" , Andi Kleen , Gerd Knorr , Dave Jones , Zachary Amsden , Pavel Machek , Andrew Morton , Linux Kernel Mailing List , Zwane Mwaikambo , Pratap Subrahmanyam , Christopher Li , "Eric W. Biederman" , Ingo Molnar Subject: Re: [patch] SMP alternatives Message-ID: <20051123222056.GA25078@nevyn.them.org> Mail-Followup-To: Linus Torvalds , Alan Cox , "H. Peter Anvin" , Andi Kleen , Gerd Knorr , Dave Jones , Zachary Amsden , Pavel Machek , Andrew Morton , Linux Kernel Mailing List , Zwane Mwaikambo , Pratap Subrahmanyam , Christopher Li , "Eric W. Biederman" , Ingo Molnar References: <1132764133.7268.51.camel@localhost.localdomain> <20051123163906.GF20775@brahms.suse.de> <1132766489.7268.71.camel@localhost.localdomain> <4384AECC.1030403@zytor.com> <1132782245.13095.4.camel@localhost.localdomain> <20051123214835.GA24044@nevyn.them.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.8i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1615 Lines: 42 On Wed, Nov 23, 2005 at 02:19:08PM -0800, Linus Torvalds wrote: > > > On Wed, 23 Nov 2005, Daniel Jacobowitz wrote: > > > > I don't think I see the point. This would let you optimize for the > > "multi-threaded, but hasn't created any threads yet" or even > > "multi-threaded, but not right now" cases. But those really aren't the > > interesting case to optimize for - that's the equivalent of supporting > > CPU hotplug. > > NO. > > There is not a _single_ compiler that is multi-threaded, and I'd argue > that there probably never will be. It's pointless. > > There's a _lot_ of really performance-sensitive stuff that will NEVER EVER > be threaded. You may run a hundred copies of them at the same time, but > every single copy will be single-threaded. > > And this will optimize that case in a BIG way. > > This is _not_ about "CPU hotplug". This is _not_ about "threaded apps > before they are threaded". This is all about the fact that serious > computation is done single-threaded, and anybody who thinks that > single-threading is going away is so totally out to lunch that it's not > even fun. I get the feeling you didn't read my message at all. Let me try it again. Why should we use a silicon based solution for this, when I posit that there are simpler and equally effective userspace solutions? -- Daniel Jacobowitz CodeSourcery, LLC - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/